Which president was the youngest ever elected?

Which presidents have been impeached by the House of Representatives? Who was the first president to be impeached? Which president was impeached twice? Which president served the shortest time in office? Which president was the youngest ever to take office, at age 42? Which president lived to age 100, the longest-lived in U.S. history? Which president was the first to live in the White House? During which president's term did the British burn the White House in 1814?